Being sent from pillar to post

Trying to actually go the correct answers out of this company after they contracted a 3rd party to handle my account, is like pulling blood from a stone. I have been sent from pillar to post after having paid the settlement amount requested by the 3rd party which I presume was communicated otherwise why would I have been provided a settlement which I paid immediately. Now I am being told that the amount remains outstanding and even manual payments made are not reflecting. Clearly the left hand doesn’t know what the right hand is doing and as a client with this company previously and for many years, I am appalled that customers are greatly this poorly.